Electromagnetic actuator and method of making same



y 20, 1965 J. A. HARPER 3,196,322

ELECTROMAGNETIC ACTUATOR AND METHQD OF MAKING SAME Filed Aug. 5, 1963mnwvvme J? A. l wper- United States Patent 3,196,322 ELECTROMAGNETICACTUATQR AND METHOD 0F MAKING SAME Jay A. Harper, Gardens, Calii-l,assignor to Acme Machine Works, Inc., Hawthorne, Calif., a corporationof California Filed Aug. 5, 1963, Ser. No. 299,798 9 Claims. (Cl.317-186) This invention relates to electromagnetic actuators such asrelays and solenoids and, more particularly, relates to such a devicefor use on aircraft where the available current is 115 volt 400 cycleA.C. current. The invention is specifically directed to the problem ofreducing the size, and especially the weight, of such a device.

For the purpose of simplifying the invention and teaching the principlesinvolved, the present disclosure is directed to what is termed afour-pole double-throw power transfer relay capable of exerting anactuating force on the order of 3 /2 pounds. The description of thisparticular embodiment of the invention will provide adequate guidancefor those skilled in the art who may have occasion to apply the sameprinciples to other specific purposes. All of the prevalent types ofaircraft relays for use with 400 cycle current are provided withrectifiers and typically are further provided with magnetic shielding,the magnetic shielding usually being provided by encasing the relay in ahousing made of magnetic steel. Rectification of the AC. current isnecessary because the core losses rise rapidly with increase in thefrequency, and these losses have heretofore become intolerable at 400c.p.s. The problem is made more difficult, moreover, because a nominalfrequency of 400 c.p.s. means in practice as high as 480 c.p.s. and, insome instances, above 500 c.p.s.

The present invention is based in large part on the discovery that, ifcertain critical requirements are met, an efficient and exceptionallylightweight relay may be designed for highly successful use in a 115volt 400 cycle circuit without the necessity of rectifying the current.The elimination of rectifiers not only reduces weight and cost but alsoincreases reliability. The invention is based in further part of theconcept of constructing such a relay with What may be termed a closedcore structure, which effectively confines the magnetic field and thusmakes it unnecessary to provide an external ferromagnetic shield.Instead, the relay is encased in a lightweight nonmagnetic metal such asaluminum. A relay constructed in accord with these teachings will occupyonly a fraction of the volume required for a conventional 400 cyclerelay, will save about one-fifth or less of the space, and will becorrespondingly lightweight.

One requirement for a successful embodiment of such a relay is that thecore material have a higher magnetic saturation point than the siliconsteels that are ordinarily used. Conventional core material, such as 3%silicon steel, has an induction saturation point of approximately 20,000gauss. The required higher saturation point may be provided, forexample, by an appropriately processed, grain-oriented alloy containingat least 49% iron and at least 49% cobalt. Such an alloy is sold byAllegheny Ludlum Steel Corporation under the trade name iermendur.Vanadium Permendur, containing approximately 2% vanadium, is preferred.The manner in which such an alloy is processed for grain orientation iswell known. The required heat treatment for removing impurities is alsowell known, and this service may be supplied by MetallurgicalConsultants, Inc., 8100 E. Slauson, Montebello, California. Therequirements for annealing 2V Permendur are as follows:

(1) Must be in pure hydrogen atmosphere at all times.

Dew point of hydrogen must be less than 40 F.

gen atmosphere and cooling rate must prevail to F.

A second requirement is that the core structure of the relay be made ofthin laminations of a particular thickness. Thickness is critical andmust not depart substantially from 0.004 inch i0.001 inch.

With further reference to the requirements for a successful embodimentof the relay, it has been found that the described core structure mustbe tightly compacted for necessary intimate metal-to-metal contactbetween the laminated jacket and the two laminated end washers. As willbe explained, this requirement may be met by suitably encasing thejacket and end washers under permanent compression.

in the preferred embodiment of the relay, both the circumferentialjacket of the core structure and the armature inside the core structureare of generally circular cross section. In this regard, a furtherrequirement for success is that both the jacket and the armature be ofspiral or tape-wound laminated construction.

In the preferred practice of the invention, the coil of the relay iswound on a suitable bobbin, and the bobbin is enclosed by a corestructure comprising a circumferential laminated jacket and twolaminated end washers. An important feature of the invention is that,with such a core structure forming closed magnetic flux paths, externalshielding becomes unnecessary, and a relay may be fabricated with a thinaluminum housing at considerable saving in weight in comparison withconventional relays.

The features and advantages of the invention may be understood from thefollowing detailed description and the accompanying drawing.

In the drawing, which is to be regarded as merely illustrative:

FIG. 1 is a longitudinal sectional view of the presently preferredembodiment of the relay;

FIG. 2 is a transverse section taken along the line 2-2 and showing thefour switches that are included in the relay construction;

FIG. 3 is a front end elevation along the line 3-3 of FIG. 1; and

FIG. 4 is a perspective view of a pressure plate that is operated by thearmature of the relay for the purpose of actuating the switches.

The selected embodiment of the relay shown in FIGS. l-4 is hermeticallyenclosed in a suitable housing, which, in this instance, comprises acup-shaped aluminum shell it) closed by an end wall 12 of suitableplastic material. The aluminum shell is provided in the usual mannerwith apertured mounting flanges or ears 15.

Since this particular relay is a four-pole, double-throw relay, thehousing encloses four single-pole, doublethrow switches 14 of awell-known snap-acting type, each of which has an operating button orplunger 15. The four switches 14 are rigidly mounted in the aluminumshell 10 by suitable bracket means 16. Mounted in the end wall 12 is aplurality of electrical terminal elements 17 which are connected to theswitches by suitable wires (not shown).

The relay proper comprises a coil 18 and an axial armature 22 whichcarries a pressure plate 24 for depressing the operating buttons 15 ofthe switches 14. The coil 18 is wound on a bobbin of suitable plastic ofthe relay as seen 0 material which has a cylindrical wall 26, an endwall 28, and two radial end flanges 30 and 32.

For successful operation of the relay, it is essential are made ofnonmagnetic metal.

that the core structure be a laminated structure of an alloy having aninduction saturation point substantially above the 20,000 gausssaturation point of a conventional grain-oriented 3% silicon alloy. Thepreviously mentioned alloy comprising at least 49% cobalt and 49% ironsatisfies this requirement, since it has a saturation induction point onthe order of 24,000 gauss. In the preferred practice of the invention,Vanadium Fermendur, supplied by Allegheny Ludlum Steel Corporation,Pittsburgh, Pennsylvania, is used, which alloy contains approximately49% each of cobalt and iron, with about 2% vanadium. For successfuloperation of the relay on 115 volt, 400 cycle, alternating currentwithout the use of rectification, the specified alloy must have athickness of 0.004 inch +0001 inch. As heretofore indicated, it isfurther essential that the laminated core structure and the laminatedarmature both be tape wound.

The core structure comprises a laminated circumferential jacket 40, alaminated pole face washer 42, and a laminated end washer 44. The poleface washer 42 is formed with an axial aperture id and comprises a stackof thin disks of the selected alloy. The end washer 44 has a large axialaperture id to clear the armature 22 and, in like manner, comprises astack of thin disks of the selected alloy. The circumferential jacket 40comprises a thin ribbon of the selected alloy of uniform width which istape wound, i.e., helically wound upon itself. It is essentialthat thecircumferential jacket 40 be in intimate contact with both the pole facewasher and the end washer 44. In the construction shown, thecircumferential jacket 40 embraces the two washers 42 and 44, and thewhole core assembly is permanently confined under pressure against theenclosed bobbin. a

The means for confining the core structure is in the form of an innercasing which is fixedly embraced by the alumintn. shell The casingcomprises an inner cylinder and a cooperating fiat ring 50, both ofwhich The inner cylinder 48 tightly embraces the tap-wound jacket i andis formed with a radially inward flange 52 at one of its ends, whichflange not only overhangs the end of the jacket 40 but also overhangs acircumferential marginal portion of the pole face Washer 42. The flatring 50 extends over the second end of the circumferential jacket 40 andadditionally overlies a circ .mferential marginal portion of the endwasher I The end of the inner cylinder 48 is turned inwardly, asindicated at 54, into engagement with the outer surface of the flat ring50. in the assembly procedure, the core structure is axially compressedagainst the end flange 52 or" inner cylinder and then the opposite ofthe is nor cyl er is swaged inwardly into engagement with the ring at tohold the core assembly under permanent axial compression. Thus thebobbin nd the two Washers T2 and id constitute an axial assembiy whichis permanently under axial com ression between the flange 52 and thering of the inner casing. This construction insures and maintainsintimate and adequate metal-to-metal contact between the jacket and thetwo washers i-L and i l.

T he armature is wound onto a short tube 55 and is fixedly bonded to thetube. The interior or" the short tube 55 is screw-threaded forengagement with the screw thread an axial rod 56, which axial rodcarries the previously mounted pressure plate A su ble coil spring 55%en ounds the rod is in compression between the pole face washer and theshort tube 55' to bias the armature to the left, as viewed in PEG. l,the limit position of the armature being determined by abutment of thepressure plate 24 against the outer side of the pole face washer as maybe seen in PEG. 1. The threaded end of'the axial rod es inside the shorttube 55 is provided with a socket or is otherwise formed fcrengagementby a screw driver or other tool to permit rotational adjust ment of theaxial rod in the assembly procedure. Conarnat ctly for operation of thefour switc res M. The fact the laminated core strwture forms cl sedpaths for the magnetic link, with the lami d aetal components of thecore structure 1'; intained under permanent axial compression formaximum. metal-to-metal contact, makes it to employ a housing of steelor other magnetic material fora shielding purpose. In effect; the corestructure is self-shielding and thus makes it possible to use aluminumand/ or plastic for the housing with substantial saving in weight.

My description in specific detail of the selected embodiment of theinvention will suggest various changes, utions, and other departuresfrom my disclosure l.n1- the spirit and scope ofthe appended claims.

1 claim:

ll. An electromagnetic actuator for operation by 320 480 cycle A.C.current without rectification, havin":

a bobbin;

a coil embracing the bobbin;

' a core structure comprising laminated end washers at the two endsrespectively of the bobbin and a laminated spirally wound jacketsurrounding the coil and the bobbin;

an armature inside the nated construction,

said core structure and armature being made of grainoriented alloyhaving an induction saturation point substantially above 20,000gauss,the laminations of the alloy being of a thickness on the order of 0.003inch to 0.005 inch; and

a casing enclosing the core structure and confining the core structureunder pressure against the bobbin.

2. An electromagnetic actuator as set forth in claim 1, in which saidalloy contains at least approximately 49% each of iron and cobalt.

3. An electromagnetic actuator as set forth in claim 2, in which theremainder of the alloy is essentially vanadiuin. I

4. An electromagnetic actuator for operation by 320 480 cycle A.C.current without rectification, having:

a bobbin;

a coil embracing the bobbin;

a core structure comprising laminated face washers at the opposite endsof the bobbin and a laminated jacket surrounding the coil and thebobbin;

an armature inside the bobbin;

said packet and said armature being spirally wound,

said core structure and armature being made of grainoriented alloyhaving an induction saturation point substantially above 20,000 gauss,the laminations of the alloy being of a thickness on the order of 0.003

inch to 0.005 inch; and

a casing enclosing the core structure and compressing the core structureaxially against the opposite ends of the bobbin, said casing comprisinga shell embracing the jacket and a cooperating end member, the shellhaving a radially inward flange at one of its ends engaging one end ofthe core structure, the end member engaging the other end of the corestructure, the other end of the shell being turned radially inward inconfining engagement with the outer side of the end member.

5. An electromagnetic actuator for operation by 320- cycle AC. currentwithout rectification, having:

a bobbin;

a coil embracing the bobbin;

a core structure comprising laminated face washers at the opposite endsof the bobbin and a laminated armature inside the bobbin,

said jacket and said armature being spirally wound,

said core structure and armature being made of grainoriented alloyhaving an induction saturation point bobbin of spirally wound lami-3,196,322 6 substantially above 20,000 gauss, the laminations of saidother end of the cylindrical member being deformed the alloy being of athickness on the order of 0.003 inwardly into overhanging engagementwith the outer inch to 0.005 inch; and face of the circular member.

a casing enclosing the core structure in a snug manner and compressingthe core structure axially against the opposite ends of the bobbin.

6. An electromagnetic actuator as set forth in claim 5,

in which said casing is preloaded to maintain the core structure underaxial compression.

5 netic actuator, characterized by the steps of:

winding a coil on a bobbin having radial flanges;

placing two stacks of thin disks of ferromagnetic material ofsubstantially the same diameter as the bobbin flat against the oppositeends of the bobbin to form 7. An electromagnetic actuator for operationgby 320- 10 therewith an axial assembly;

480 cycle A.C. current without rectification, having: winding around theaxial assembly a ferromagnetic a bobbin with radial flanges at itsopposite ends; tape of uniform width substantially equal to the axial acoil embracing the bobbin inside the diameter of dimension of the axialassembly to form a laminated the radial flanges; jacket embracing theaxial assembly in intimate a laminated armature mounted for axialmovement contact with the two stacks of disks;

inside the bobbin; placing a circular member against the one end of thetwo stacks of disks lying against the opposite ends of axial assembly;

the bobbin against the radial flanges thereof, all of forming acylindrical casing of an inside diameter the disks being ofsubstantially the diameter as the substantially equal to the outsidediameter of the radial flanges of the bobbin, at least one of the twoaxial assembly with an integral radially inward stacks having an axialopening to accommodate flange at one end of the cylindrical casing;

axial movement of the armatuure; telescoping the cylindrical casing overthe axial assema tape of uniform width equal to the axial dimension blyand the circular member with the inward flange of the bobbin plus theaxial dimensions of the two of the cylindrical casing abutting the otherend of the stacks of disks, the tape being spirally wound around axialassembly;

the bobbin and the two stacks of disks to form a placing the circularmember together with the axial jacket confining the two stacks of disks;assembly and the inward flange of the cylindrical the laminations of thearmature as well as the disks casing under axial compression; and

and the tape being made of a grain-oriented alloy while the axialcompression is maintained, deforming having an induction saturationpoint substantially the other end of the cylindrical casing inward intoabove 20,000 gauss and being of a thickness on the overhangingengagement with the circular member order of 0.003 inch to 0.005 inch;to make the axial compression permanent. a cylindrical easing embracingthe jacket and holding the jacket in intimate contact with thecircumfer- References Citfii y the Examine! ential edges of the flangesof the bobbin and with UNITED STATES PATENTS the confined stacks ofdisks, said casing having radial- 1y inward flanges at its opposite endsoverlapping 3050563 8/62 Zlpper 317-186 circumferential margins of thetwo stacks and co- OTHER REFERENCES operating to compress the two stacksagainst the two ends of the bobbin Gould et al.: Supermendur, a NewRectangular- Loop Magnetic Material, Electrical Engineering, March 1957,pages 208-211.

8. A combination as set forth in claim 7 in which the casing comprises acylindrical member with an integral radially inward flange at one endand a circular member embraced by the other end of the cylindricalmember, LARAMIE ASKIN' Primary Examiner

1. AN ELECTROMAGNETIC ACTUATOR FOR OPERATION BY 320480 CYCLE A.C.CURRENT WITHOUT RECTIFICATION, HAVING: A BOBBIN; A COIL EMBRACING THEBOBBIN; A CORE STRUCTURE COMPRISING LAMINATED END WASHERS AT THE TWOENDS RESPECTIVELY OF THE BOBBIN AND A LAMINATED SPIRALLY WOUND JACKETSURROUNDING THE COIL AND THE BOBBIN; AN ARMATURE INSIDE THE BOBBIN OFSPIRALLY WOUND LAMINATED CONSTRUCTION, SAID CORE STRUCTURE AND ARMATUREBEING MADE OF GRAINORIENTED ALLOY HAVING AN INDUCTION SATURATION POINTSUBSTANTIALLY ABOVE 20,000 GAUSS, THE LAMINATIONS OF THE ALLOY BEING OFA THICKNESS ON THE ORDER OF 0.003 INCH TO 0.005 INCH; AND A CASINGENCLOSING THE CORE STRUCTURE AND CONFINING THE CORE STRUCTURE UNDERPRESSURE AGAINST THE BOBBIN.